Lathroeus Thomson, 1864

Monné, Miguel A. & Santos-Silva, Antonio, 2020, Synonymies, transferences and redescriptions in Neotropical Acanthocinini (Coleoptera, Cerambycidae, Lamiinae), Zootaxa 4851 (3), pp. 593-600 : 594

Lathroeus Thomson, 1864

Lathroeus Thomson, 1864: 25 ; Lacordaire, 1872: 764; Gemminger, 1873: 3149 (cat.); Breuning, 1967: 846 (cat.); Monné, 1995: 62 (cat.); 2001: 180; 2005: 54 (cat.); 2012: 70; 2020: 68 (cat.).

Lathraeus ; Thomson, 1865: 354 (error).

Anisopodesthes Melzer, 1931: 66 ; Monné, 1995: 67 (cat.); 2005: 16 (cat.); 2012: 66; 2020: 15 (cat.). Syn. nov.

Thomson (1864) described Lathroeus as follows (translated): “Genus near Anisopodus , but differs by prothorax with lateral tubercle obtuse, and hind legs and tarsi shorter; antennae 11-segmented, longer than body, scape and antennomere III subequal, remaining antennomeres gradually shorter; elytra wide, depressed, lateral margin abruptly inclined, centrobasal crest with short tuft of setae, elytral apex bispinose; prosternal process and mesoventral process laminiform; metafemora not reaching elytral apex; metatarsomere I slightly elongate.”

Melzer (1931) described Anisopodesthes as follows (translated): “Genus near Anisopodus . Body elongated, depressed, narrowed posteriorly; head concave between antennae; frons short, transverse, flat; base of antennal tubercles distant from each other; eyes coarsely faceted, strongly emarginated, upper eye lobes moderately distant from each other, lower eye lobes large, subquadrate; genae very small; antennae elongate, slender, with long setae ventrally on basal segments, 11-segmented, scape elongate, antennomere III slightly shorter than scape; thoracic width briefer, laterally behind middle rounded expanded, moderately narrowed toward anterior region, pronotal disc unequal; elytra basally wider than prothorax, elongate, depressed, gradually narrowed toward apex; apex obliquely concave, with acute angles; humeral carina acute; anterobasal crests moderately elevated, with black setae dorsally; hind legs elongate, metafemora distinctly clavate, surpassing elytral apex; metatarsi moderately elongate, metatarsomere I as long as II and III together; prosternal process narrow, widened posteriorly; mesoventral process barely wider, flat.”

Curiously, both, Thomson (1864) and Melzer (1931) thought their genera were similar to Anisopodus White, 1855 . Melzer (1931) also compared Anisopodesthes to Lathroeus (translated): “Due to some features (absence of thoracic spines, pronotum not smooth on disc, etc.) there is some affinity with the genus Lathroeus Thoms. , but the excessive length of the hind legs clearly distinguishes it.”

However, as also occurs in other genera of Acanthocinini , the length (and often shape) of metafemora is variable, and when alone, does not allow to separate genera. As all other features present in Anisopodesthes also occur in Lathroeus , the former is considered a junior synonym.

Lathroeus can be recognized by the following set of features: antennae 11- segmented, distinctly longer than body; eyes coarsely faceted; antennal tubercles distant from each other; sides of prothorax with rounded gibbosity about middle (from slight to distinctly projected); pronotal disc tuberculate or, at least, with distinct gibbosities; elytra without erect setae; base of elytra distinctly wider than prothorax; humeral carina well marked from humerus to outer apical angle; elytral dorsal carina absent or slightly marked; elytra with outer apical angle spiniform or projected; centrobasal crest present on elytra; prosternal process and mesoventral process narrow; femora clavate.

Bates (1863) divided Alcidion Thomson, 1860 into two groups: “It is divisible into two groups, — one of which is distinguished by the species having a raised line along the whole length of the elytra on each side, from the centrobasal ridge to the external apical angle; and the other by the absence of these lines, the centrobasal ridges at the same time being very prominent.”

Monné (1977) replaced Alcidion Thomson (not Alcidion Sturm, 1843 ) as Nealcidion , redescribed the genus keeping the two groups of species proposed by Bates (1863), and added a third group (translated): “Group I ( Bates 1863: 105), with dorsal carina on elytra, from centrobasal crest to outer elytral apex”; “Group II ( Bates 1863: 105), lacking dorsal and lateral carinae on elytra”; “Group III, with lateral carina on anterior 2/3 or 3/4 of the elytra, sometimes with dorsal carinae slightly distinct.”

Lathroeus differs from Nealcidion (group I) especially by the absence of dorsal carina on elytra from anterior area to outer apical angle (present in Nealcidion (group I)). The species of the groups II and III of Nealcidion encompasses a mess of species not possible to separate without a full revision of the genus. For now, provisionally Lathroeus can be separated from the species of group II (sensu Monné 1977) by the presence of humeral carina (absent in Nealcidion (group II)); and from the species of group III (sensu Monné 1977) by the humeral carina reaching outer apical angle (reaching 2/3 or 3/ 4 in Nealcidion (group III)). According to this, it is possible that all species with humeral carina belong to Lathroeus .